Name: _______________________
BBE 1002: Biorenewable Resources
Homework 4 (due Tuesday April 28, 2015)
Use three significant digits in your answers. Box your answers, and indicate units if applicable.
1. A chemical composition study of wheat straw reveals that it contains 34.5% hexosan (mostly glucan
from cellulose) and 22.1% pentosans (mostly from hemicellulose xylans) based on dry mass. The
remainders are lignin, extractives, and ash.
a. (10 points) Calculate the theoretical (maximum) ethanol yield (in gallon per dry ton or gallon/bdt) of
wheat straw. Note: 1bdt = 2,000 lb
b. (10 points) Estimate the actual ethanol yields (in gallon/bdt) based on the following information:
Conversion and recovery efficiency: 80% for hexosan; 90% for pentosan
Monomeric sugar fermentation efficiency: 75% for hexose; 55% for pentose
c. (5 points) Estimate the ethanol potential (in gallon/year) if there are 20 millions dry tons of wheat
straws available every year. Hint: you need to use your answer from part (b) and common sense.
2. You have been assigned the task of calculating the heat values of wood under the following
conditions:
Moisture content (wet basis) – 35%;
Species: hardwood;
Efficiency of combustion furnace: 68%.
a. (6 points) Determine the gross heating value in Btu per lb of wood at 35% wet-basis MC.
b. (4 points) Calculate the recoverable heat (in Btu/lb) from combusting wood at 35% wet-basis MC.
c. (4 points) Calculate the amount of recoverable heat (in Btu) from combusting 800 lb of wood at the
same MC as above.
3. An electricity generator plant consumes a daily supply of 300 metric ton (mt) of green resinous
softwood chips of 40% moisture content (wet basis). Note: 1 mt equals 1,000 kg.
a. (5 points) How much is the estimated gross heating value from each kilogram of wood at 40% wetbasis MC? Provide your answer in kJ/kg.
b. (6 points) If the generator efficiency is 30%, how much electrical energy (in kJ/day) could be
generated from the wood?